1. Field of the Invention
The present invention relates to a method for producing non-woven fabrics or paper-like materials having excellent properties by a wet method from fibers comprising hydroxymethyl cellulose xanthate, namely, a derivative of cellulose xanthate.
2. Description of the Prior Art
Hydroxymethyl cellulose xanthate is a methylolation product of cellulose xanthate. Its fibers are strongly acidic and stable, but are characterized by quite high chemical reactivity. These types of fibers and a method for producing non-woven fabrics or paper-like materials from the fibers are disclosed in U.S. Pat. No. 3,718,537 and U.S. Ser. No. 267,994 filed June 30, 1972, now U.S. Pat. No. 3,832,281 (corresponding to Italian Pat. No. 962,732).
These types of fibers have not heretofore been entirely successfully used in a wet process preparation of non-woven fabrics or paper-like materials, and it is now believed that the prior failures are attributable to an inability to properly disperse or distribute the fibers in water. The use of dispersing accelerators have been considered, but heretofore, the high reactivity of the fibers have hindered effective use of such agents. It has now been discovered that a suitable such agent must have the properties of being:
1. acidic PA1 2. highly water-soluble PA1 3. essentially chemically non-reactive with the fibers and cause no denaturation of the fibers PA1 4. highly stable with respect to polyethylene oxide, polyacrylamide or the like, which are often used as dispersion stabilizing agents. PA1 i. change in electric charge of the fiber surface caused by the surfactant, PA1 ii. adsorbability of the surfactant onto the fiber surface, and PA1 iii. reduction in abrasion resistance by lubricating agent's effect in water. PA1 a. dispersing spun and stretched viscose fibers comprising hydroxymethyl cellulose xanthate in an aqueous medium having a pH of lower than 6.0 at a temperature of lower than 30.degree.C, PA1 b. forming the dispersed fibers into a web by a wet forming method, PA1 c. dehydrating the web to the extent that the water content of the web becomes lower than 700%, said fibers after dehydration being characterized by: PA1 d. subjecting at least a portion of the surface of dehydrated web to a pressure of greater than 2 Kg/cm at a temperature of 90.degree. to 180.degree.C, thereby fusing and decomposing the hydroxymethyl cellulose xanthate in the pressed portion of the fibers and simultaneously bonding the fibers in said portions to each other, and PA1 e. subjecting the pressed web to regeneration treatment to decompose the remaining hydroxymethyl cellulose xanthate into cellulose.
Accordingly, a need continues to exist for an improved wet process technique of forming non-woven fabrics or paper-like materials from hydroxymethyl cellulose xanthate fibers.